diff options
Diffstat (limited to 'lisp/userlock.el')
| -rw-r--r-- | lisp/userlock.el | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/lisp/userlock.el b/lisp/userlock.el index a0c55fd1e13..1cfc3b9d64a 100644 --- a/lisp/userlock.el +++ b/lisp/userlock.el @@ -97,6 +97,41 @@ You can <q>uit; don't modify this file.") (define-error 'file-supersession nil 'file-error) +(defun userlock--check-content-unchanged (fn) + (with-demoted-errors "Unchanged content check: %S" + ;; Even tho we receive `fn', we know that `fn' refers to the current + ;; buffer's file. + (cl-assert (equal fn (expand-file-name buffer-file-truename))) + ;; Note: rather than read the file and compare to the buffer, we could save + ;; the buffer and compare to the file, but for encrypted data this + ;; wouldn't work well (and would risk exposing the data). + (save-restriction + (widen) + (let ((buf (current-buffer)) + (cs buffer-file-coding-system) + (start (point-min)) + (end (point-max))) + ;; FIXME: To avoid a slow `insert-file-contents' on large or + ;; remote files, it'd be good to include file size in the + ;; "visited-modtime" check. + (when (with-temp-buffer + (let ((coding-system-for-read cs) + (non-essential t)) + (insert-file-contents fn)) + (when (= (buffer-size) (- end start)) ;Minor optimization. + (= 0 (let ((case-fold-search nil)) + (compare-buffer-substrings + buf start end + (current-buffer) (point-min) (point-max)))))) + (set-visited-file-modtime) + 'unchanged))))) + +;;;###autoload +(defun userlock--ask-user-about-supersession-threat (fn) + ;; Called from filelock.c. + (unless (userlock--check-content-unchanged fn) + (ask-user-about-supersession-threat fn))) + ;;;###autoload (defun ask-user-about-supersession-threat (fn) "Ask a user who is about to modify an obsolete buffer what to do. |